Fg, FFg, FFFg used to describe: (PGI June 2007)

Ans. C (Black gunpowder) FG, FFG, FFFG .... are used to discribe the size of grains of black gunpowderQGunpowder used in FirearmsBlack PowderQ It consists of Potassium nitrate 75%, Charcoal 15% & Sulphur 10% (Pnemonic - PCS in decreasing percentage) It is designated as FG, FFG, FFFG, etc., depending on size of the grains. More the no. of F's, the finer are grains & the faster the burning. The powder grains are black, coarse or fine, without any particular shape. It burn with production of much heat, flame & smoke. The gas consists of CO. CO2 N2, H2S, H2, CH4 etc., all at a very high temperature.Smokeless powderQ It consists of nitrocellulose (guncotton) or nitroglycerine & nitrocellulose (double-base). Triple base powder consists of nitrocellulose, nitroglycerine & nitroguanidine.They produce much less flame & smoke & more completely burnt than black powder.Semismoke less powderQ It is a mixture of 80% black & 20% of smokeless powder.